PROCEEDINGS ARTICLE | November 30, 2001
Proc. SPIE. 10302, Optoelectronic Information Processing: Optics for Information Systems: A Critical Review
KEYWORDS: Fabry–Perot interferometers, Quantum wells, Modulation, Phase shift keying, Modulators, Computer programming, Spatial light modulators, Optoelectronics, Optical correlators, Amplitude modulation
To be competitive with their electronic counterparts, correlation-based optical processors require very fast spatial light modulators (SLMs) that can perform simultaneously phase and amplitude modulation. Owing to their ultra-high speed, multiple quantum well (MQW) SLMs have been early identified as very good candidates. However, the coding domain of MQW SLMs is not widely known. We present here a study of available coding domains of MQW SLMs. We demonstrate that pure amplitude modulation, ternary { -1, 0, + 1} modulation and quaternary {0, + 1, ei2π/3, ei4π/3}, modulation are examples of coding domains that can be achieved by tuning a few parameters in the design of Fabry-Perot MQW modulators. We show that ternary and quaternary filters provide much better results than binary filters for the recognition of objects embedded in highly cluttered noise. Finally, we present a technique, the time-averaged pseudo-random encoding technique, which enables encoding of any complex filter onto a quaternary modulator. Combined with the time-averaged pseudo-random encoding technique, MQW SLMs may pave the way to the development of new optoelectronic correlator systems with improved speed and accuracy performance.
